Enhanced flow boiling heat transfer in embedded hybrid distributed jet/pin-fin microchannel heat sink

Abstract

An embedded hybrid distributed jet/pin–fin microchannel (JPM) heat sink with flow boiling visualization is constructed in the silicon base to enhance the chip-level heat dissipation. The flow boiling heat transfer characteristics of deionized water in JPM heat sink with jet Reynolds numbers (Re_j) of 244 ∼ 732 and inlet subcoolings (ΔT_sub) of 20°C ∼ 60°C are experimentally investigated and compared with those in distributed jet/smooth microchannel (JSM) heat sink. Two-phase flow patterns in JPM and JSM are simultaneously captured by a high-speed microscope camera. It is found that compared with JSM, critical heat fluxes for JPM are significantly enhanced by 27.7 %∼70.8 % due to the effective prevention of reverse flow and local dry-out. Specifically, JPM achieves an extremely high critical heat flux of 1098 W/cm² at a small pressure drop of 4.2 kPa when Re_j = 732 and ΔT_sub = 40°C. Moreover, JPM can increase the heat transfer coefficient by 33.4 %∼51.6 % and decrease the effective thermal resistance by 22.8 %∼32.1 % due to more nucleation sites and larger heat transfer surfaces existing in JPM than in JSM. Meanwhile, better flow boiling stability and base temperature uniformity are obtained for JPM because its pin–fin structures can enhance the flow disturbance, promote the phase uniform distribution, and prevent the reverse flow. Particularly note that, although the enhancement in heat transfer is at the cost of the increase in pressure drop, JPM has superior comprehensive thermal–hydraulic performance than JSM, with PECs for JPM compared to JSM being 1.18 ∼ 1.29 under different conditions. This study provides a more efficient embedded two-phase electronic cooling scheme by combining pin–fin microchannel with distributed jet impingement.